Mario Circuit is the first track to compete in the Flower Cup in Mario Kart Wii. The track's overview is slightly similar to Figure-8 Circuit from Mario Kart DS, having two main bends and two straight stretches. It takes place in a town in front of Princess Peach's Castle. Some supporting characters from the Mario game series like Hammer Bros., Shy Guys and Sledge Bros appear watching the race. Other characters such as Goombas or a Chain Chomp serve as obstacles within the course. This is also where the Award Ceremony takes place at the end of any race or cup.

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Competitors start out the race in the town, going downhill through a straight stretch. On the straight stretch is the first set of item boxes, laid out straight just like the other courses. Audience members, such as Shy Guys and Hammer Bros. can be seen on the left and right side of the straightaway, waving at the racers. On the first curve to the left are a few Goombas who waddle on the road, spinning out any players who come in contact with them. After some Goombas is a little twist in the roads and another set of item boxes.

Up ahead, the players can see two paths to take. One is on the ramp with the boost panel on it, on the right side of the Chain Chomp off-road. It can be used and the players can do a stunt on that ramp, but gaining too much speed may lose control and the players may bump into a wall to slow down even more, or possibly get hit by the Chain Chomp. Another path is around the left of the Chain Chomp, which is the main path of the course. The right lane is dangerous to go in; the Chain Chomp's attacks will reach as far as this lane. After the curve around the Chain Chomp is an overhang, crossing the lane above where the race started previously.

On the left turn after the overhang are a few item boxes moving from left and right, unlike the stationary item boxes seen earlier. The path is very straight until a curve left, which has some more Goombas waddling around as seen in the very first stretch of the course. After the curve and the Goombas is another straight road, and if the players continue driving straight, they'll see the finish line and start the cycle again.

Towards the middle-end of the track, there is a boost ramp that will allow the driver to fly over the dirt and behind the Chain Chomp. This provides a significant boost but it does require a Mushroom, Mega Mushroom, Golden Mushroom, or a Star to access it without losing time. Recently, a way has been discovered to do this without a Mushroom by releasing a mini-turbo right before the curb.

There are two Staff Ghosts. One is available from the start with a time of 01:44.777. This ghost uses Mario on the Zip Zip. The second one is unlocked by getting a time of 01:40.378 or less and that ghost has a time of 01:33.702. This ghost uses Mario on the Sprinter.

A different kind of tournament took place on this track for February 2010's second tournament. In it, players had to take out sixteen Goombas with Green Shells and Stars. It was restricted to karts only. It was repeated as the tournaments for October 2011's second tournament, December 2012's second tournament, and March 2014's first tournament, with the restrictions removed for the October and March tournaments.